Detecting alcohol-impaired drivers has gained a high level of importance during the last decade. In most cases, the reason to identify alcohol-impaired individuals participating in public traffic is motivated by safety issues and legal implications caused by these individuals operating cars, machinery or other equipment. Safety and legal issues are both very important in the context of a mobile society heavily relying on motorized vehicles for transportation. Financial implications for individuals or groups of the society resulting from accidents are considerable. Recognizing the importance of these facts, the abatement of alcohol-related accidents has been identified as prime target by the U.S. government.
Conventional technology utilized for alcohol (also referred to herein as ethanol or ethyl alcohol, CH.sub.3 CH.sub.2 OH) detection in traffic and traffic related situations relies on two different approaches:
1. Screening for blood alcohol is used to determine whether an individual's blood alcohol content (BAC) is below or above a certain threshold value. In most cases, screening is done by means of breath analysis to establish the breath alcohol content (BrAC). Conversion factors have been established to convert BrAC values into BAC values. The most commonly accepted conversion factor is 2100 (A. W. Jones, "Precision, Accuracy and Relevance of Breath Alcohol Measurements", Modern Problems of Pharmacopsychiatry, Vol. 11, pp. 65-78, 1976). Although breath analyzers are used frequently in traffic control situations, e.g., at sobriety checkpoints or for random screening of equipment operators, they only yield initial results to justify further evidential blood alcohol tests. PA1 2. Evidential blood alcohol testing is the method of choice to establish legally-binding BAC values and, normally, is required after a positive breath alcohol test result. For the purpose of evidential alcohol tests, breath analysis with certified breath analyzers, chemical urine analysis, or blood sample analysis are most commonly employed. However, these methods, especially urine and blood tests, are time-consuming, require expensive equipment and trained operators and may necessitate medical supervision. PA1 (a) Only selected vehicles can be tested for alcohol-impaired drivers due to logistical and personnel limitations, allowing a high percent rate of drivers under the influence to continue to drive. PA1 (b) Vehicles with drivers suspected to be under the influence have to be stopped, necessitating costly sobriety checkpoints and follow-up examinations. PA1 (c) Expensive equipment has to be setup and maintained at high cost. PA1 (d) Human interaction is required, accounting for a variety of different problems, e.g., high personnel costs, risk of violent encounters, etc. PA1 (e) Testing is sporadic and does not provide continuous monitoring of the driver's condition with respect to the ingestion of alcohol. PA1 1. Fuel Cells: Fuel cell sensor devices are based on electrochemical reactions, in which alcohol in the gas phase is oxidized on a catalytic electrode surface to generate a quantitative electrical response. Sample gas is injected or drawn into the detector causing system response proportional to the alcohol concentration in the gas sample. PA1 2. Semiconductors: Sensors of this type utilize small, heated (300.degree. C.) beads of a transition metal oxide, across which a voltage is applied to produce a small standing current. The magnitude of this current is determined by the conductivity of the surface of the bead. Since the conductivity is affected by the amount of alcohol molecules adsorbed, it can be taken as a measure for the alcohol concentration in the gas sample. PA1 3. Infrared Absorption: Absorption devices for breath sampling operate on the principle of infrared light being absorbed by alcohol molecules. The amount of light absorbed by the gas sample flowing though the sample cell can be taken as a measure of the alcohol content. PA1 4. Gas Chromatography: This technique uses the ability of inorganic compounds to retain gas molecules on their surface in a characteristic way for different species. The retention time of alcohol in a separating column filled with the compound is used for its identification, the magnitude of detector response can be taken as a measure for the alcohol concentration in the gas sample. PA1 5. Colorimetry: Devices based on this effect make use of the color change some chemicals display when reacting with alcohol. A gas sample is drawn into a small glass tube filled with a substrate containing an acidified solution of potassium dichromate. In the presence of alcohol, the color of the substrate changes from yellow to green. The length of the discolored portion of the tube can be taken as a measure for the alcohol concentration of the sample. PA1 (a) a laser comprising a gain medium having two opposed facets within a laser resonator and functioning as an intracavity spectroscopic device having a first end and a second end, the first end operatively associated with a partially reflecting (i.e., partially transmitting) surface; PA1 (b) a reflective or dispersive optical element (e.g., a mirror or a diffraction grating) operatively associated with the second end to define a broadband wave-length laser resonator between the optical element and the first end and to thereby define an external cavity region between at least one facet of the gain medium and either the first end or the second end or both ends; PA1 (c) the external cavity region being exposed to a sample of air representative of the air in the cabin of the vehicle to enable any ethyl alcohol molecules to enter thereinto; PA1 (d) a detector spaced from the first end and providing an output detector signal; PA1 (e) appropriate electronics for measuring and analyzing the detector signal; PA1 (f) a housing for containing at least the laser, the partially reflecting surface, and the optical element, the housing being configured to prevent escape of stray radiation into the cabin and to permit air from the cabin to continuously circulate through the external cavity region for analysis; and PA1 (g) means for driving the laser (e.g., electrical or optical). PA1 (1) sensing any ethyl alcohol vapors in the vehicle by the on-board sensor; PA1 (2) providing a signal indicative of presence of any ethyl alcohol vapors.
Both of the above approaches are based on technologies which can only be applied external to a vehicle and require the cooperation of tested individuals with authorities conducting the alcohol test. Besides these commonalities, both approaches share several significant shortcomings:
These facts lead to the conclusion, that (i) conventional technologies available to identify alcohol-impaired drivers are limited in their applicability and (ii) due to their conceptual shortcomings, these methods are even less suited to contribute to a significant further reduction of alcohol abuse in traffic as required by the government.
There are a number of technologies that are used for alcohol detection in gas samples. The following operational principles can be found in most commercial breath analyzers:
None of these devices has yet fulfilled the simultaneous requirements of fast response, high sensitivity, and continuous on-board monitoring in a moving vehicle. Thus, they are only utilized as the result of driver intervention by law enforcement personnel.
A new generation of small, highly-sensitive, on-board alcohol detectors would help to greatly reduce the number of alcohol-impaired drivers by preventing individuals under the influence from driving vehicles. These sensors, mounted within the cabin area of vehicles, would address the problem of driving under the influence before it even arises.